Bottle Trap

Enchant creature
Miniscule (At the beginning of your end step, put a -1/-0 counter on enchanted creature. When enchanted creature has a base power of 0, put a colorless artifact token called Mystic Cruiser with "{1}, {t}: Put a -1/-0 counter on target creature.").
Whenever you control two or more Mystic Cruisers, you may sacrifice enchanted creature: If you do, you gain 20 life.